1. Field of the Invention
The present invention relates to thin-film magnetic writing heads used in, for example, floating magnetic heads. In particular, the present invention relates to a thin-film magnetic head having reduced inductance suitable for high recording densities and to a method for making the thin-film magnetic head.
2. Description of the Related Art
FIG. 18 is a partial front view of a conventional thin-film magnetic head (inductive head). FIG. 19 is a partial cross-sectional view taken along line XIXxe2x80x94XIX and viewed from arrows in FIG. 18.
The thin-film magnetic head has a lower core layer 1 formed of a magnetic material such as permalloy, and an insulating layer 9 formed thereon. The insulating layer 9 has a groove 9a which extends from a face opposing a recording medium (hereinafter referred to as ABS (air bearing surface)) in the height direction (Y direction in the drawings) and has a track width Tw. A lower magnetic pole layer 3 magnetically coupled with the lower core layer 1, a gap layer 4, and an upper magnetic pole layer 5 are formed in that order by plating in the groove 9a. As shown in FIG. 19, a coil layer 7 having a spiral pattern is provided on the insulating layer 9 behind the groove 9a in the height direction (Y direction in the drawing). The coil layer 7 is covered with a coil insulating layer 8 composed of, for example, a resist. An upper core layer 6 is formed on the coil insulating layer 8. The upper core layer 6 is magnetically coupled with the upper magnetic pole layer 5 at a leading end 6a and with the lower core layer 1 at a base portion 6b. 
In the inductive head shown in FIGS. 18 and 19, a recording current applied to the coil layer 7 induces recording magnetic fields in the lower core layer 1 and the upper core layer 6. These recording magnetic fields generate a fringing magnetic field between the lower magnetic pole layer 3 magnetically coupled with the lower core layer 1 and the upper magnetic pole layer 5 magnetically coupled with the upper core layer 6. The fringing magnetic field records magnetic signals on a recording medium such as a hard disk.
In this inductive head, the lower magnetic pole layer 3, the gap layer 4, and the upper magnetic pole layer 5 have a track width Tw. This inductive head is suitable for narrow tracks at the ABS.
A method for making the inductive head will be described. The insulating layer 9 is formed on the lower core layer 1, the groove 9a having the track width Tw and a predetermined length is formed in the insulating layer 9 in the height direction from the ABS. The lower magnetic pole layer 3, the gap layer 4, and the upper magnetic pole layer 5 are formed by plating in that order in the groove 9a, and the coil layer 7 is formed by patterning on the insulating layer 9 behind the groove 9a. 
The coil layer 7 is covered with the coil insulating layer 8. The upper core layer 6 is formed by a frame plating process over the upper magnetic pole layer 5 and the coil insulating layer 8. The inductive head shown in FIGS. 18 and 19 is thereby completed.
Trends toward narrower track widths accompanying high recording densities and high recording frequencies require reduced inductance of inductive heads. The reduced inductance requires a reduced magnetic path length, which is formed from the lower core layer 1 to the upper core layer 6. Thus, the width T1 of the coil layer 7 lying from the leading end 6a to the base portion 6b must be decreased. By decreasing the width T1 of the coil layer 7, the length of the upper core layer 6 is also decreased, and thus the magnetic path length is decreased.
A possible solution for decreasing the width T1 of the coil layer 7 without changing the number of turns of the coil layer 7 is to use a double-layer structure for the coil layer 7. However, in the structure of the thin-film magnetic head shown in FIGS. 18 and 19, the magnetic path length cannot be decreased to a level suitable for future higher recording frequencies even if the coil layer 7 has a double-layer structure. As a result, the inductance cannot be reduced to a required level.
The reason for the above insufficiently reduced inductance is that the coil layer 7 is formed on the thick insulating layer 9. As shown in FIG. 18, the insulating layer 9 has a thickness H5, which is larger than the total thickness H6 of the lower magnetic pole layer 3, the gap layer 4, and the upper magnetic pole layer 5. Thus, the coil layer 7 on the insulating layer 9 lies, as shown in FIG. 19, above a reference plane between the upper magnetic pole layer 5 and the upper core layer 6, that is, the coil layer 7 is shifted toward the upper core layer 6.
When the coil layer 7 has a double-layer structure, the height from the upper face of the lower core layer 1 to the upper face of the coil insulating layer 8 becomes significantly large regardless of a decreased width T1 of the coil layer 7. Accordingly, the magnetic path length is not decreased as expected, and the inductance is not decreased to a required level.
Moreover, the double-layer configuration of the coil layer 7 inevitably causes an increased thickness H1 of the coil insulating layer 8 covering the coil layer 7. The protrusion of the coil insulating layer 8 from the reference plane is significant. Thus, the pattern of the upper core layer 6 is not readily formed by a frame plating process over the upper magnetic pole layer 5 and the coil insulating layer 8. As a result, the upper core layer 6 cannot be formed to a predetermined shape, particularly in the vicinity of the leading end 6a. 
When the width T2 of each conductive turn of the coil layer 7 is reduced and the thickness H2 of each conductive turn is increased, the volume of the coil layer 7 does not vary. Thus, the width T2 of each conductive turn can be reduced without increased coil resistance. Thus, the overall width T1 of the coil layer 7 can be reduced so that the magnetic path length is further decreased. As a result, inductance is further reduced.
However, since the thickness H2 of each conductive turn is increased, the protrusion of the coil insulating layer 8 covering the coil layer 7 is more significant. Thus, the upper core layer 6 cannot be formed into a required pattern.
Accordingly, it is an object of the present invention to provide a thin-film magnetic head having reduced inductance by a narrow track and a decreased magnetic path length and a method for making the thin-film magnetic head.
A thin-film magnetic head in accordance with the present invention includes a lower core layer, an upper core layer, a track width defining portion, and a first coil layer. The lower core layer may have an optional lower magnetic pole layer thereon. The upper core layer may have an optional upper magnetic pole layer thereunder. The track width defining portion defines a size in a track width direction disposed between the lower core layer and the upper core layer at a face opposing a recording medium the air bearing surface (ABS). The first coil layer induces recording magnetic fields in the lower core layer and the upper core layer. The first coil layer has a spiral conductive pattern with a predetermined number of turns. The track width defining portion includes a gap layer and at least one of the lower and upper magnetic pole layers. The lower magnetic pole layer is in contact with the lower core layer. The upper magnetic pole layer is in contact with the upper core layer. The gap layer is provided between the lower core layer and the upper core layer for insulating the lower core layer and the upper core layer. The first coil layer is provided behind the track width defining portion in a height direction. The upper face of the first coil layer is aligned in a reference plane defined by the interface between the track width defining portion and the upper core layer. A gap between turns of the spiral conductive pattern of the first coil layer is filled with a lower first-coil insulating layer. An upper first-coil insulating layer is formed on the first coil layer. Moreover, the upper core layer is provided over the track width defining portion to the upper first-coil insulating layer. The base portion of the upper core layer is magnetically coupled with the lower core layer.
In the present invention, the first coil layer is formed at a position which differs from the position of a coil in a conventional thin-film magnetic head to decrease the magnetic path length and thus decrease inductance. Accordingly, the thin-film magnetic head is suitable for future higher recording densities and higher recording frequencies.
The first coil layer is disposed behind the track width defining portion in the height direction. The surface of the first coil layer is aligned in the reference plane defined by the interface between the track width defining portion and the upper core layer. That is, the first coil layer is formed at a lower position compared to a conventional thin-film magnetic head. The height from the upper face of the lower core layer to the upper face of the upper coil-insulating layer is decreased. Thus, the length of the upper core layer is decreased, resulting in a decreased magnetic path length and decreased inductance.
Since the upper face of the first coil layer is aligned in the reference plane, the thickness of the first coil layer can be maximized. Thus, the width of the spiral conductor of the first coil layer can be reduced depending on the thickness without increasing the resistance. Moreover, the increased thickness contributes to a decreased magnetic path length and decreased inductance.
Preferably, the first coil layer comprises a conductive layer and a protective layer provided thereon. The top surface of the protective layer is aligned in the reference plane.
Since the protective layer can protect the conductive layer of the first coil layer from oxidation, the resistance of the first coil layer is maintained at a predetermined value.
Preferably, the conductive layer comprises at least one nonmagnetic conductive layer including at least one element of Cu and Au. The protective layer comprises at least one nonmagnetic conductive layer including at least one element selected from the group consisting of Ni, P, Pd, Pt, B, Au, and W.
Preferably, the lower first-coil insulating layer comprises an inorganic material.
Preferably, the thin-film magnetic head further includes a second coil layer on the upper first-coil insulating layer and a second-coil insulating layer for covering the second coil layer. The second coil layer is electrically connected to the first coil layer. The upper core layer is formed over the track width defining portion to the second-coil insulating layer. This configuration facilitates a further reduction in the width of the coil layers. As a result, the inductance is further decreased due to the further decreased magnetic path length.
Preferably, the upper face of a first coil center of the first coil layer is aligned in the reference plane and the first coil center of the first coil layer is electrically connected to a second coil center of the second coil layer.
Preferably, the gap layer comprises a nonmagnetic metal material formable by plating. In this case, the nonmagnetic metal material preferably comprises at least one material selected from the group consisting of NiP, NiPd, NiW, NiMo, NiRh, Au, Pt, Rh, Pd, Ru, and Cr.
A method for making a thin-film magnetic head in accordance with the present invention is described.
In the first step, a track width defining portion is formed on a lower core layer. The track width defining portion includes one of the following combinations: (1) the lower magnetic pole layer, the nonmagnetic gap layer, and the upper magnetic pole layer; (2) the lower magnetic pole layer and the nonmagnetic gap layer; and (3) the nonmagnetic gap layer and the upper magnetic pole layer. The track width defining portion has a predetermined length from a face opposing a recording medium (ABS) in the height direction.
In the second step, an insulating underlayer is formed on the lower core layer behind the track width defining portion in the height direction. A first coil layer is formed on the insulating underlayer.
In the third step, a lower first-coil insulating layer is formed and covers the track width defining portion and the first coil layer.
In the fourth step, the upper face of the lower first-coil insulating layer is planarized. The upper face of the track width defining portion and the upper face of the first coil layer are in the same plane and are exposed from the surface of the lower first-coil insulating layer.
In the fifth step, an upper first-coil insulating layer is formed on the exposed first coil layer.
In the sixth step, an upper core layer is formed the track width defining portion to the upper first-coil insulating layer.
In this method according to the present invention, the track width defining portion including the magnetic pole layer and the gap layer is formed on the lower core layer at the face opposing the recording medium (ABS) at a predetermined length in the height direction. Thus, the insulating layer 9 shown in FIGS. 18 and 19 is not present behind the track width defining portion. The lower core layer can be formed on the thin insulating underlayer provided on the lower core layer behind the track width defining portion. Consequently, the height from the upper face of the lower core layer to the upper face of the coil layer can be decreased. Accordingly, the thin-film magnetic head exhibits decreased inductance due to a decreased magnetic path length.
In this method, the first coil layer is formed on the insulating underlayer by patterning up to a position which is higher than the upper face of the track width defining portion after the upper face of the lower first coil insulating layer is planarized, then the lower first-coil insulating layer is polished by a CMP (chemical-mechanical polishing) process to expose the track width defining portion and the upper face of the coil layer. According to this method, the thickness of the first coil layer can be maximized. Thus, the width of the first coil layer can be reduced to decrease the magnetic path length without increased resistance.
Preferably, the first coil layer comprises a coil layer and a protective layer formed thereon. The protective layer is exposed from the lower first-coil insulating layer when the upper face of the lower first coil insulating layer is planarized.
Preferably, the conductive layer comprises at least one nonmagnetic conductive layer including at least one element of Cu and Au. The protective layer comprises at least one nonmagnetic conductive layer including at least one element selected from the group consisting of Ni, P, Pd, Pt, B, Au, and W.
Preferably, an inorganic insulating layer is formed as the lower first-coil insulating layer. Preferably, the track width defining portion, the first coil layer, and the inorganic insulating layer are planarized so that these layers are alinged in the same plane.
Preferably, the method further includes a step of forming a second coil layer electrically connected to the first coil layer and forming a second-coil insulating layer on the second coil layer after the upper first-coil insulating layer is formed. Preferably, the upper core layer is formed on the upper first-coil insulating layer covering the second coil layer. This configuration facilitates a further reduction in the width of the coil layers. As a result, the inductance is further decreased due to the further decreased magnetic path length.
Preferably, when the upper face of the lower first-coil insulating layer is planarized, a coil center of the first coil layer is exposed. A coil center of the second coil layer is deposited on the first coil center.
Preferably, when the track width defining portion is formed, the gap layer is formed together with at least one of the upper and lower magnetic pole layers by plating. In this case, the gap layer preferably comprises at least one material selected from the group consisting of NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.